The following U.S. patents are believed to be generally relevant to the field of the invention:
5,396,583 3/1995 Chen et al 395/127 5,446,833 3/1995 Miller et al 395/125
Panoramic images of scenes are used to provide a viewer with an immersive surround experience, as if the viewer was standing in the center of a scene gazing in several directions. Panoramic images can be produced by taking multiple snapshots of a scene, as a camera is rotated horizontally and possibly also vertically. The snapshots are stitched together and projected onto an appropriate geometrical surface, such as a cylinder or sphere, to reproduce an omniview effect.
Digital panoramic images are used inter alia to provide virtual reality experiences over the Internet. These images are normally stored on a host computer, or server, and accessed by users over the Internet. Software panorama production tools take digital snapshots as inputs, and numerically stitch them together and project them onto an appropriate curved surface. The digital snapshots may come from a digital camera, or from scanned in-pictures. An example of a software system used to produce panoramic images is assignee's PHOTOVISTA.TM. product, which can be accessed at EQU http://www.livepicture.com.
Interactive panorama viewers comprise software that enables a client computer to display a portion of the panorama, so that a user sees a corresponding part of the surrounding scene. The viewers carry out perspective geometry transformations that project the panorama onto a view window. Although only a portion of the scene can be displayed within the view window, the panoramic viewer enables the user to interactively navigate the scene. User navigation includes (i) panning in several directions, which translates the viewable portion of the scene, and (ii) zooming in and out, which magnifies and reduces the scene, effectively changing the field of view. An example of a panorama viewer is assignee's LIVE PICTURE.TM. Viewer product, which can be accessed at EQU http://www.livepicture.com.
To enable efficient implementations of interactive zooming within large images over the Internet, some software applications today are using multi-resolution tiled image formats. Multi-resolution tiled images are constructed by first creating multiple copies of the image at different resolutions. Moreover, at each resolution the image is partitioned into a collection of tiles.
FLASHPIX.RTM., a registered trademark of the Digital Imaging Group (DIG), is an example of a multi-resolution tiled image format A FlashPix image is constructed by starting with an original image and recursively sub-sampling it at half the resolution. The recursion continues until the final sub-sampled image is reduced to 64 pixels or less in each dimension. Each image level is partitioned into tiles that are 64.times.64 pixels in size. A reference for FLASHPIX.RTM. is a document "FlashPix Format Specification," .COPYRGT.1996, 1997, Eastman Kodak Company, the contents of which are hereby incorporated by reference.
To illustrate the advantages of multi-resolution tiled image formats, suppose a client with a viewing window of 640.times.480 pixels desires to view an image whose full resolution is 15,000.times.15,000 pixels. The client is unable to view the full image at its original resolution, and can either view the complete image at a low resolution, or view only a portion of the image at a high resolution. Usually the user prefers to begin with an initial view showing the full image at a low resolution, and then to interactively navigate by zooming, i.e., increasing the resolution while decreasing the "field of view," or the portion of the image being viewed, and panning, i.e. translating the current view.
In order for a FlashPix image server to respond with an image at 640.times.480 pixel resolution that contains the full original image which is sub-sampled, an appropriate close pre-computed resolution is determined. Using the above dimensions, the successive resolutions are 15,000.times.15,000 pixels, then 7,500.times.7,500 pixels, then 3,750.times.3,750 pixels, then 1,875.times.1,875 pixels, then 937.times.937 pixels, etc. For example, the image server can choose an image level of 937.times.937 pixels and re-sample to 640.times.480 pixels. This is far better than re-sampling the full 15,000.times.15,000 pixel image because it requires far less processing.
FlashPix images are more complicated than simple raster images. The individual 64.times.64 pixel tiles into which each image level is partitioned are usually JPEG compressed for Internet applications. Furthermore, the FlashPix format specification requires that the tiles be stored within a Microsoft OLE structured storage file. Structured storage files are compound files composed of multiple storages and streams, where storages are analogous to folders/directories and streams are analogous to files. Although there is overhead in accessing information inside a structured storage file, such files provide a clean interface for a complicated file structure. Structured storage is referenced in Appendix A of the above-referenced FlashPix Format Specification.
Assignee's co-pending U.S. patent application Ser. No. 08/647,018 filed May 8, 1996 and entitled RENDERING PERSPECTIVE VIEWS OF A SCENE USING A SCANLINE-COHERENT LOOK-UP TABLE, the disclosure of which is hereby incorporated by reference, discloses a panorama viewing method and system. It describes an efficient way to provide pan and zoom navigational capabilities, so as to enable a user to have a smooth experience as the user interactively views panoramic images. To ensure smooth navigation it is important that the rendering be optimized so as to yield successive frame data at a refresh rate of approximately 30 frames/second.
Assignee's co-pending U.S. patent application Ser. No. 08/922,732 filed Sep. 3, 1997 and entitled A METHOD AND SYSTEM FOR COMPOSITING IMAGES, the disclosure of which is hereby incorporated by reference, describes a way to stitch panoramic snapshots together in a way that compensates for possible different lighting conditions in each snapshot. To reproduce an original scene, it is important that there be no visible signs of stitching between successive snapshots.
Assignee's co-pending U.S. patent application Ser. No. 09/055,038 filed Apr. 3, 1998 and entitled A METHOD AND SYSTEM FOR PANEL ALIGNMENT IN PANORAMAS, the disclosure of which is hereby incorporated by reference, describes a way to embed images within a panorama so as to match the curvature of the panorama.